﻿INVERTEBRATES. 
  289 
  

  

  sliping 
  side 
  of 
  the 
  right 
  posterior 
  radial, 
  the 
  second 
  and 
  third 
  are 
  

   smaller, 
  one 
  resting 
  on 
  the 
  top 
  of 
  the 
  left 
  posterior 
  subradial, 
  and 
  

   the 
  other 
  on 
  the 
  first 
  anal. 
  

  

  Column 
  rather 
  stout, 
  the 
  upper 
  joints 
  filling 
  nearly 
  the 
  whole 
  

   concavity 
  of 
  the 
  base, 
  and 
  composed 
  of 
  thick 
  and 
  thinner 
  joints 
  

   alternately 
  arranged. 
  

  

  Position 
  and 
  locality: 
  Warsaw 
  beds 
  of 
  the 
  St. 
  Louis 
  group, 
  near 
  

   Clayton, 
  Adams 
  county, 
  111. 
  

  

  No. 
  2,460, 
  Illinois 
  State 
  collection. 
  

  

  Poteriocrinus 
  Illinoiensis, 
  Worthen. 
  

  

  PI. 
  XXVIII, 
  Pig. 
  17. 
  

   Poteriocrinus 
  Illinoiensis, 
  Woethen, 
  Feb. 
  1882. 
  

   Bulletin 
  No. 
  1, 
  of 
  the 
  Illinois 
  State 
  Museum 
  of 
  Natural 
  History, 
  p. 
  19. 
  

  

  Body 
  of 
  medium 
  size, 
  obconical, 
  gradually 
  tapering 
  from 
  the 
  sum- 
  

   mit 
  of 
  the 
  radials 
  to 
  the 
  base. 
  

  

  Basal 
  plates 
  of 
  moderate 
  size, 
  projecting 
  more 
  than 
  half 
  their 
  

   length 
  beyond 
  the 
  column, 
  and 
  forming 
  by 
  themselves 
  a 
  low, 
  pen- 
  

   tagonal 
  cup. 
  

  

  Subradials 
  as 
  large 
  or 
  larger 
  than 
  the 
  radials, 
  two 
  on 
  the 
  pos- 
  

   terior 
  side 
  heptagonal, 
  the 
  others 
  hexagonal. 
  

  

  Radials 
  rather 
  wider 
  than 
  long, 
  pentagonal, 
  and 
  truncated 
  squarely 
  

   across 
  their 
  upper 
  margins 
  for 
  the 
  reception 
  of 
  the 
  brachial 
  series. 
  

  

  Brachials 
  rather 
  smaller 
  than 
  the 
  radials, 
  pentagonal, 
  a 
  little 
  con- 
  

   stricted 
  above, 
  the 
  upper 
  angle 
  obtuse, 
  and 
  giving 
  support 
  to 
  the 
  

   first 
  divisions 
  of 
  the 
  rays. 
  The 
  arms 
  are 
  not 
  preserved, 
  in 
  the 
  only 
  

   specimen 
  yet 
  .found 
  of 
  this 
  species, 
  but 
  from 
  the 
  very 
  narrow 
  plates 
  

   that 
  are 
  to 
  be 
  seen 
  in 
  one 
  of 
  the 
  rays, 
  they 
  probably 
  continue 
  sim- 
  

   ple 
  above 
  the 
  first 
  division 
  on 
  the 
  brachial 
  series. 
  

  

  Eirst 
  anal 
  plate 
  longer 
  than 
  wide, 
  pentagonal, 
  and 
  resting 
  be- 
  

   tween 
  two 
  of 
  the 
  subradials, 
  and 
  partly 
  under 
  the 
  right 
  posterior 
  

   radial. 
  Second 
  anal 
  larger 
  than 
  the 
  first, 
  hexagonal, 
  and 
  resting 
  

   on 
  the 
  summit 
  of 
  the 
  left 
  posterior 
  subradial. 
  Third 
  anal 
  smaller 
  

   than 
  the 
  first, 
  on 
  which 
  it 
  rests, 
  and 
  above 
  this 
  a 
  double 
  series 
  of 
  

   small 
  plates 
  are 
  partly 
  visible, 
  that 
  probably 
  formed 
  the 
  base 
  of 
  the 
  

   ventral 
  tube. 
  

  

  Column 
  round, 
  and 
  near 
  the 
  base 
  composed 
  of 
  joints 
  nearly 
  equal 
  

   in 
  thickness. 
  

  

  Geological 
  position 
  and 
  locality: 
  Warsaw 
  beds 
  of 
  the 
  St. 
  Louis 
  

   group, 
  Warsaw, 
  Illinois. 
  

  

  No. 
  2,457, 
  Illinois 
  State 
  collection. 
  

  

  —19 
  

  

  